The Universal Serial Bus (USB) has become the standard for connectivity of personal computers, notebook or laptop computers and related devices, to peripherals devices, such as printers, external memory devices, speakers, scanners, cameras, smart phones, mp3 players and the like. Standard USB hubs serve to extend the availability of USB connections on a single device and are generally configured with four USB connectivity ports (in a non externally powered USB hub) and up to about seven ports.
The ports of the USB hub conventionally function as “upstream” and “downstream” USB ports, with one port being designated as the upstream port which is connected to a controlling device such as a PC, also known as the “master’ or “host”. The other remaining ports are downstream to the hub and PC, and are used to connect to peripherals, designated as “slave” devices. Common master-slave functions include printing by printers, as directed by PCs, exchange of data (download and upload) of data between memory devices and a PC, as controlled by the PC, and download of songs to mp3 devices as selected and controlled by the PC.
Over the past decade, devices such as cell phones and smart phones in particular and similar devices (the iPad® tablet, book readers from various sources, PDAs, etc.) have proliferated, with USB ports (usually with a mini USB port connection). These devices have useful functions as both controlled slave devices, such as with synchronized connection with PCs, and as master or host devices for connection with peripherals such as memory storage devices. A protocol was developed for these type of devices, in 2001 (with wider availability by 2004), known as USB On-The-Go (OTG), wherein devices such as cell phones (or cradles associated therewith), equipped with OTG elements, could automatically assume either a master (controlling) function when connected to a peripheral device such as a memory card or a slave (peripheral) function, when connected to a master PC, such as for synchronization. Other OTG devices include the aforementioned electronic tablets, book readers, and PDAs, as well as mp3 players, cameras, card readers, printers, dvd reader/writers and the like. It is, however, specifically recognized in the field that OTG host/peripheral (master/slave) function swapping works only with a one-to-one connection and does not work through a standard USB hub.
With the use of a standard USB hub, the connected OTG device is frozen into a single function depending on its upstream/downstream port connection with the hub. As a result, the OTG device may become a simple host, without possibility of operative connection to another host such as a PC. Thus, if such a hub is connected to an OTG device, all the downstream ports are now purely host ports, and therefore one can no longer connect to a host port, with OTG functionality being lost and the entire system behaving as a host only.